Method of mining thick coal seams by longwalling and conveying



S p 1969 R. e. MALLANDER METHOD OF MINING THICK GOAL SEAMS BY LONGWALLING AND CONVEYING Filed March 25, 96

2 Sheets-Sheet 1 F G 8 INVENTQR.

RICHARD G. MALLANDER Sept. 16, 1969 R. s. MALLANDER 3,

METHOD OF MINING THICK COAL SEAMS BY LONGWALLING AND CONVEYING Filed March 25, 1968 2 Sheets-Sheet 2 :ila

FlG 2 United States Patent US. Cl. 299-11 6 Claims ABSTRACT OF THE DISCLOSURE The face of the bottom layer of a thick underground coal seam is mined to an extent by conventional longwall mining. Conveyors are positioned rearward of and parallel to the face of coal being mined. The longwall mining operation is halted and the coal above the conveyors is caved onto the conveyors which are positioned to carry the coal caved thereon laterally of the direction of longwalling. The conveying continues until substantially all of the coal caved thereon is removed. The longwalling operation is repeated and the conveyors are advanced with the longwalling operation. The coal above the conveyors is caved onto the conveyors and removed as previous. The longwalling, caving, and removing operations continue until a chosen length of the coal seam is mined.

BACKGROUND OF THE INVENTION This invention relates to mining, and, more particularly, to a method of mining thick seams of coal.

In the past, the full mining of thick underground coal seams (i.e., thicker than about feet) has not been attempted. This is so for two reasons: (1) The removal of the roof or overburden (which in some cases may be 300 feet thick) to expose the coal for surface mining is such a time-consuming job that mining the coal in such manner is not economically feasible. (2) Underground mining of the full depth of the seam (with the roof in place) creates great safety problems, because of the difliculty of controlling the caving of the roof. Consequently, to a great extent, the coal in such thick seams remains unmined, resulting in a waste of resources.

It is an object of this invention to provide a method of underground mining of thick coal seams.

It is a further object of this invention to provide a method of underground mining of thick coal seams which is extremely safe while being economical and effective.

SUMMARY OF THE INVENTION Broadly stated, this method of mining coal from a thick seam beneath a roof comprises exposing a face of coal in the bottom layer of the seam, under and spaced from the roof, and removing coal along but spaced from the roof to advance the face thereof. The coal and roof thereon are supported only immediately behind the face. Means are provided for conveying coal laterally of the direction of advance of the face immediately behind the supported coal and roof thereon. The coal and roof thereon are caved onto the conveying means, and at least some of the coal caved on the conveying means is conveyed laterally of the direction of advance of the face.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects of the invention will become apparent from a study of the following description and drawings, in which:

FIG. 1 is a broken plan view of a mine showing the mining operation of this invention;

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FIG. 2 is a sectional view of the mine of FIG. 1 showing the installation of longwalling apparatus;

FIG. 3 is a view similar to FIG. 2 but showing the installation of the trailing conveyors;

FIG. 4 is a view similar to FIG. 3 but showing coal caved onto the trailing conveyors;

FIG. 5 is a view similar to FIG. 4 but showing the coal being conveyed by the trailing conveyors;

FIG. 6 is a view similar to FIG. 5 but further along in the conveying operation;

FIG. 7 is a view similar to FIG. 6 but showing the advance of the face of the coal and the trailing conveyors;

FIG. 8 is a view similar to FIG. 6 but showing the coal being mined further along the seam.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 there is shown the conventional longwalling of a bottom layer (about 8-10 feet thick) of a coal seam 10 of depth anywhere from, for example, 30 to feet thick. The longwalling is done from an entry 12 to an entry 14 and along an entry 16. The entries 12, 14, 16 are kept open by suitable props (as for example 18). The longwalling commences from entry 12, with props 20 acting to support the coal seam 10 and overburden or roof 22, which may in some cases be 300 feet thick. A conventioinal cutting machine 24 travels along the face of the coal seam 10 exposed by the props 20 and cuts away the face of the bottom layer of the coal seam, thereby advancing the face of the coal seam 10.

The coal cut away in this manner i transported to entry 16 by means of a conveyor 26 which is positioned along the face of the coal seam. The removed coal is then carried through the entry 16 to a main shaft (not shown) through which it is removed from the mine.

After the cutter 24 has made a complete cut across the face of the coal seam 10, the props 20 are moved toward the advanced face to continue support of the coal seam 10 and roof 22 thereon. The cutter 24 and conveyor 26 are also advanced forwardly into proper position.

When sutficient advance of the face of the coal seam 10 (and of the conveyor 26 and props 20) has been made, a number of trailing conveyors 28 are installed immediately behind the props 20 (FIG. 3). These conveyors 28 are positioned to convey material thereon laterally of the direction of advance of the coal seam 10 toward the entry 16. The longwalling operation is tem porarily halted, and the coal (and roof thereon) directly above the conveyors 28 is caved onto the conveyors 28 (FIG. 4). The coal may be caved by drilling and blasting if needed. The conveyors 28 are then set in motion, and the coal caved thereon is conveyed thereby to a conveyor 30 in entry 16, by which it is carried to the main shaft. The movement of each conveyor 28 may be adjusted so that proper removal of substantially all of the caved coal takes place. This is shown in FIGS. 5-6. The amount of coal and composition of material being removed by each conveyor 28 may be observed in entry 16, and the movement of each conveyor 28 may be controlled so that substantially the full depth of the coal in that area is mined without also removing any of the overburden lying on top of the caved-in coal seam.

When the desired amount of caved coal has been mined, the longwalling operation commences, and the face of the coal seam 10 is advanced along with the props 20 and conveyor 26. As the props 20 advance the conveyors 28 are advanced with it (FIG. 7). This continues until the conveyors 28 are clear of the remains of the caved coal and roof thereon. The longwalling operation is again temporarily halted. The coal and roof thereon directly above the conveyors 28 is caved onto the conveyors 28 (as in FIG. 4 again). The conveyors 28 are then used to convey substantially all of the coal caved thereon to entry 16, as described previously.

The face, conveyor 26, props 20, and conveyors 28 are advanced, and coal is caved onto and conveyed by conveyors 28 (FIG. 8) until a desired length of coal seam 10 has been fully mined.

As noted previously, the conveyors 28 are advanced with the pIOps 20. This is facilitated by impact hammers which ride on the conveyor 28 closest the props 20. The frequency of impact can be adjusted to insure that proper advance of the conveyors 28 takes place. The natural flushing action of the caved material will also assist in advancing the conveyors (FIG. 8).

It has been found that the process disclosed herein can be applied with advantage to the mining of certain types of hard rock.

It will be seen that herein is provided an effective and safe way of mining the full depth of a thick coal seam. Furthermore, the process is extremely economical since (a) the mining takes place underground, so that the roof need not be removed, and (b) the full depth of a coal seam is mined in a single pass of the equipment.

Having thus described my invention, I claim:

1. A method of mining coal from a seam beneath a roof comprising:

(a) exposing a face of coal under and spaced from the roof;

(b) removing coal along but spaced from the roof to advance the face thereof;

(c) supporting the coal and roof thereon only immediately behind the face;

((1) providing means for conveying coal laterally of the direction of advance of the face immediately behind the supported coal and roof thereon;

(e) caving the coal and roof thereon onto the conveying means; and

(f) conveying at least some of the coal caved on the conveying means laterally of the direction of advance of the face.

2. A method according to claim 1 wherein the advancement of the face is halted before the coal and roof thereon are caved onto the conveying means and while the coal is conveyed thereby.

3. A method of mining coal according to claim 2 wherein the face of coal is exposed at substantially the bottom of the coal seam.

4. A method according to claim 3 wherein substantially all of the coal caved on the conveying means is conveyed.

5. A method of mining coal from a seam beneath a roof comprising:

(a) exposing a face of coal substantially at the bottom of the coal seam;

(b) removing coal along the bottom of the coal seam to advance the face thereof;

(c) supporting the coal and roof thereon only immediately behind the face;

(d) providing means for conveying coal laterally of the direction of advance of the face immediately behind the supported coal and roof thereon;

(e) halting the advancement of the face;

(f) caving the coal and roof thereon onto the conveying means;

(g) conveying substantially all of the coal caved on the conveying means laterally of the direction of advance of the face;

(h) removing coal along the bottom of the coal seam to advance the face thereof;

(i) supporting the coal and roof thereon only immediately behind the face;

(j) advancing the means for conveying coal laterally of the direction of advance of the face substantially along with the advance of the face;

(k) halting the advancement of the face and the conveying means being advanced with the face;

(1) caving the coal and roof thereon onto the conveying means; and

(m) conveying substantially all of the coal caved on the conveying means laterally of the directioin of advance of the face.

6. A method according to claim 5 wherein the method steps (h)-(m) are repeated until a desired length of the coal seam is mined.

References Cited UNITED STATES PATENTS 1,583,992 5/1926 OToole 29944 1,588,987 6/1926 OToole 29911 1,770,934 7/1930 Ievin 299l8 ERNEST R. PURSER, Primary Examiner US. Cl. X.R 

